The nitro derivatives of aromatic compound find applications in the manufacture of dyes, API's, pesticides and fine chemicals. Typically the exothermic nature of nitration of aromatic substrates does not facilitate an easy scale-up based on laboratory experiments and more precautions are taken to make the entire process safer with larger scales. Also, as it is mentioned in the analysis of industrial and laboratory nitration processes (ACS Symposium Series, 22, ACS, 1976, 201) in general the aromatic nitration is a heterogeneous system and the rate of nitration strongly depends upon the interfacial mass transfer rates and the nature of dispersion. Relative rates of mass transfer and the rate of parallel reactions affect the overall conversion as well as the selectivity of a specific isomer. Thus providing adequate heat transfer area to take care of the heat duty and provide efficient mixing to enable high diffusion rates is essential for the scale-up of nitration processes. While some of these constraints are observed while doing nitration in batch or semi-batch mode, they can be overcome effectively in continuous mode of operation.
Continuous flow nitration of organic substrates has been reported in a few patents U.S. Pat. No. 4,091,042 and U.S. Pat. No. 4,021,498 discuss the continuous adiabatic nitration of nitrobenzene. EP0436443B1 covers a continuous process for nitration of nitratable organic substrates including hydrocarbons and halogenated aromatic hydrocarbons. More recently, the patent (WO2007087816A1) based on. Corning's Advanced Flow reactor on nitration of aromatic substrates demonstrates the ability of the specific device towards nitration of a few organic and specifically aromatic substrates.